This invention relates to electronic test instruments and, more particularly, to electronic instrumentation for signal measurements during tests performed on electro-optical and/or opto-electrical systems and associated components. Specifically, the invention is directed to calibrating electronic test instruments for accurately performing such tests.
An exemplary use of the invention is in the field of optical and electrical signal measurements in connection with fiber optic systems. With higher bit rates and wider-band modulations becoming prevalent in fiber optic systems, the designers and manufacturers of these systems and associated components need to be able to characterize performance more thoroughly and more precisely than has been the case with lower transmission bandwidths. Many new fiber optic systems now operate at speeds of 500 MBPS and higher, which are equivalent to RF and low microwave frequencies. In addition, even though optical fiber cable is correctly classified as a low-loss medium, a fiber optic system can, in fact, have significant losses that must be identified if they are to be minimized. Accordingly, the test measurements performed to characterize such a system have proliferated.
Various test systems have been developed to meet these measurement needs. Techniques for calibrating these test systems for performing the desired signal measurements have also been developed to a limited extent. However, no known fiber optic test system manufacturer currently offers sources or receivers (or electro-optical and opto-electrical converters) calibrated in terms of their modulation (or demodulation) transfer characteristics. This has resulted in errors during testing.